Porcine proliferative enteropathy (PPE, also known as ileitis) is an important enteric disease of swine, causing significant morbidity and mortality in swine herds throughout the world. The name “PPE” describes a group of diseases characterized by hyperplasia of crypt enterocytes in the ileum, jejunum, and large intestine. The causative agent is Lawsonia intracellularis, a Gram-negative obligate intracellular bacterium. The disease is widespread in pigs raised under various management systems and causes significant impact worldwide. See, for example, Barker et al., “The alimentary system,” In: Jubb K V F, Kennedy P C, Palmer N, eds. Pathology of Domestic Animals. 4th ed. San Diego, Calif.: Academic Press; 1993:1-317; and McOrist and Gebhart, “Porcine proliferative enteropathies,” In: Straw B E, D'Allaire S, Mengeling W L, Taylor D J, eds. Diseases of Swine. 8th ed. Ames, Iowa: Iowa State University Press; 1999:521-534.
The main clinical manifestations of PPE include the acute form, porcine hemorrhagic enteropathy (PHE), and the chronic form, porcine intestinal adenomatosis (PIA). Porcine hemorrhagic enteropathy usually occurs in pigs four to twelve months of age, particularly replacement breeding stock. Clinical signs include loose, watery stools with blood, gauntness, and high morbidity and mortality. Stressful events, such as mixing or sorting, shipping, and overcrowding, often precede an outbreak of PHE. Porcine intestinal adenomatosis commonly occurs in postweaned pigs six to twenty weeks of age. Failure to gain weight is the usual manifestation; other signs may include mild to moderate diarrhea, dullness, and apathy. See, for example, McOrist and Gebhart, “Porcine proliferative enteropathies,” In: Straw B E, D'Allaire S, Mengeling W L, Taylor D J, eds. Diseases of Swine. 8th ed. Ames, Iowa: Iowa State University Press; 1999:521-5342.
The control of PPE is dependent in large part on the prudent administration of effective antimicrobial agents. And while an avirulent live vaccine, Enterisol®, is commercially available, there is a need for improved, economical methods for controlling L. intracellularis infections in pigs.